Lockable nut system

ABSTRACT

A lockable nut system for use with threaded steel bar which includes a screw threaded nut for engagement with the threaded steel bar and a locking member which is slidably engageable with the bar. The locking member is adapted to resist rotation about the bar and is also axially engageable with the nut to prevent rotation of the nut. The locking member has one or more fingers to engage the nut with an end of the finger being displaced to engage the nut as a result of deformation of a finger actuating tab or a dished body of the locking member. The locking member may engage the bar by displacement of an end of at least one tongue as a result of deformation of a tongue actuating tab during compression between the nut and a second structure.

This application is a divisional of U.S. patent application Ser. No.10/036,600 filed Dec. 21, 2001, now U.S. Pat. No. 6,860,688.

This invention is concerned with locking elements for threadedconnection to threaded metal bars.

Particularly, although not exclusively, this invention is concerned witha locking system for nuts used with threaded bars.

It is common practice to provide bracing support in steel and timberframed structures and foundations to form a triangulated stiffening toresist wind loads and otherwise to restrain structural memberscomprising the building and/or foundation framework. Threaded steel barsare also used as “the down” bolts for cyclone rated structures.

Typically, bracing is embodied in wall frames, across rafters and otherroofing structures and is connected to load bearing members in thestructure. Normally a combination of tension and compression members isused to form a pin jointed framework which takes wind loads from a wallstructure through the bracing framework to the foundations.

Tensionable bracing members are currently selected from:

(a) continuous threaded steel rod with a variety of attachment means;

(b) plain steel bar with welded turnbuckles;

(c) threaded steel bar with right and left hand threads on opposite endsto accommodate turnbuckles;

(d) threaded steel bar with “D” brackets.

Screw threaded bracing members have the advantage of allowing adjustableattachment of mounting members to accommodate variances in thepositioning of hold down bolts or the like as well as variances in thepositioning of supporting members such as columns or the like.

The use of screw threaded bracing members facilitates erection as theadjustable mounting permits an increase in length of the bracing memberto assist in lifting and positioning the member between connectionpoints on support members. Any sag in the brace member is removed bytensioning the member by adjustable mounts such as turnbuckles havingleft and right handed threads.

The use of adjustable bracing members thereby eliminates the necessityfor drift pins and other rigging tools commonly used to accommodatesmall variances in fixed attachment points associated with angle bracingmembers.

Notwithstanding the relative advantages and disadvantages of adjustablescrew threaded bracing members and non-adjustable angle bracing members,angle form bracing members are widely used due to the limited tensioncapacity of traditional screw threaded rods which is a function of thecapacity of the thread on the bar and/or the threaded mounting members.

In screw threaded bars where the thread is cut into the outer surface,this leads to a significant reduction in thread capacity.

In contrast, for threads produced by thread rolling processes, this lossof section is reduced somewhat as the thread is rolled up from a smallerdiameter bar and there are fewer sharp corners than in machined threadswhich weaken the bar by providing propagation points for stress failure.

Regardless of the means by which the thread is formed, tension capacityin the bar is limited to thread capacity. Moreover, the materialstrength of thread-rolled members is limited to that of a steel gradewhich can be thread-rolled on conventional thread-rolling equipmentunless the product is later subjected to heat treatment which would thenrender the product uneconomical.

Thread rolled bar is finding increasing structural applications where atensionable member is required. The relatively coarse pitch threadcompared to a machined thread requires the use of an elongate nut toprovide adequate contact area between the respective nut and barthreads.

In our co-pending Australian patent application 42532/00 there isdescribed a structural bracing system employing thread rolled steel barand tensionable end fitting for attachment of the ends of the bar to astructure and a nut locking system for use therewith. While generallysatisfactory for its intended purpose, the locking system required aseparate securing system to maintain engagement between a threaded nutand the nut locking member. This was inconvenient to manufacture andcould not be relied upon in many applications.

One problem that arises with the use of such rods is the ability of nutsengaged with such threads to loosen when subject to vibration or otherexternal forces. The use of a second threaded bar nut as a locknut isnot considered suitable as a locking arrangement as it is not possibleto obtain adequate thread compression.

Similarly, once a threaded bar is secured by a nut/locknut combination,it is not possible to loosen or tighten the bar without first undoingthe locknut.

For example, threaded rods may be used in railway foundations which aresubject to the regular hammering of rail vehicle passage. The repeatedapplication of such intermittent pressure may lead to the loosening of anut engaged with such a rod. If the nut is of particular importance tothe structural integrity of, for example, a bridge, or if a significantnumber of bolts loosen, the potential for catastrophic failure of thesystem is real and possibly high. Railway engineers often take expensiveprecautions to avoid such a situation, usually by way of avoiding nut torod engagement of this sort.

It would be of great benefit if a reliable system of locking a nut to arod was provided. Further benefits would arise if to do so involved arelatively low cost solution. Clearly, such a system would find wideapplicability in areas other than the rail and building industries.

It is an aim of the present invention to overcome or alleviate at leastsome of the disadvantages associated with prior art locking systems forthreaded couplings associated with threaded bars.

SUMMARY OF THE INVENTION

According to one aspect of the invention there is provided a lockablenut system for threaded steel bar, said lockable nut system comprising:

a screw threaded nut rotatably engageable on said threaded steel bar;and

a locking member slidably engageable on said threaded steel bar, saidlocking member being adapted in use to resist rotation about said bar,said nut and said locking member being axially engageable whereby in usesaid locking member resists rotation mat least one direction of said nuton said bar.

The locking member may be adapted to resist rotation by a screw threadedfastener extending between said locking member and a surface of saidbar.

Most preferably said locking member includes inner side walls engageablewith opposed side walls of said bar.

If required said nut and said locking member are axially engageable byone or more socket and spigot formations on respective adjacent ends ofsaid nut and said locking member.

The lockable nut system may include deformation member for engaging thenut by deforming to engage at least one recess in the nut. Thedeformation member is preferably resiliently deformable. The deformationmeans may comprise at least one nut engaging element projecting axiallyfrom a locking member and at least one actuating element deformable froma first to a second position, thereby causing the at least one nutengaging element to engage with at least one recess or seat in the nut.Preferably, the at least one nut engaging element is a finger.Preferably, the finger has one or more ramped edges. Most preferably,the nut engaging element is urged outwards relative to a longitudinalaxis of the threaded steel bar during use.

The actuating element may be one or more tabs and is preferably a pairof opposed tabs. When in a first position, the one or more tabs may beoffset from a transverse plane of the locking member.

The locking means may be adapted to resist rotation around the bar byinclusion of one or more bar engaging members. The bar engaging membermay be edges of an aperture of the locking member engageable withparallel sides of the threaded steel bar.

Alternatively, the bar engaging member may comprise at least one barengaging element projecting axially from the locking member and at leastone bar engaging actuating element deformable from a first position to asecond position and thereby urging the bar engaging element towards thethreaded steel bar. The bar engaging element may be tongue. The barengaging actuating element may be one or more tabs. The one or more tabsmay be offset from the transverse plane of the locking member when inthe first position.

The nut for the lockable nut system may include an internal perimeterwith a plurality of adjacent recesses for receiving the at least one nutengaging element. Alternatively or additionally, the nut may include anexternal perimeter with a plurality of adjacent recesses for receivingthe nut engaging element.

In a further aspect, the invention resides in a locking member for alockable nut system comprising a substantially planar body with at leastone axially projecting finger and at least one finger actuating tab,wherein, in use, deformation of the at least one finger actuating tabfrom a first to a second position urges an end of the at least onefinger in a preselected direction The preselected direction may beoutward. Preferably, the locking member further comprises at least onebar engaging tongue and at least one tongue actuating tab, wherein, inuse, deformation of the at least one tongue activating tab from a firstposition offset from a transverse plane of the body to a second positionsubstantially co-planar with the transverse plane of the body urges anend of the bar engaging tongue inwardly.

In yet a further aspect, the invention may reside in a nut for alockable nut system, said nut including a plurality of recesses forreceiving a portion of a locking nut. Preferably, the recesses aredistributed around an internal perimeter of a bore of the nut.Alternatively, the plurality of recesses may be distributed around anouter perimeter of the nut.

In order that the invention may be more fully understood and put intopractical effect, reference will now be made to preferred embodiments ofthe invention illustrated in the accompanying drawings in which:

FIG. 1 shows a preferred form of threaded steel bar for use with theinvention.

FIG. 2 shows a lockable nut system according to the invention.

FIG. 3 shows side and end views of the nut of FIG. 2.

FIG. 4 shows side and end views of the sleeve of FIG. 2.

FIG. 5 is a perspective view of a locking washer for use with a lockablenut system.

FIG. 6 is a top view of the washer of FIG. 5.

FIG. 7 is a side view of the washer of FIG. 5.

FIG. 8 is a side view of the washer of FIG. 5 orthogonal to the view ofFIG. 7.

FIG. 9 is the view of FIG. 7 with indications of operative forces duringuse.

FIG. 10 is the washer of FIG. 9 when in locking position.

FIG. 11 is an orthogonal view of the washer of FIG. 9 with indicationsof operative forces during use.

FIG. 12 is the same view as FIG. 11 when the locking washer is inlocking position.

FIG. 13 is a perspective view of a lockable nut system using the washerof FIG. 5.

FIG. 14 is a side view of the lockable nut system of FIG. 13 aligned forapplication.

FIG. 15 is a plan view of the lockable nut system of FIG. 14.

FIG. 16 is a part sectional side view of the lockable nut system of FIG.14 when engaged taken in direction of arrows AA.

FIG. 17 is a part sectional view of the lockable nut system of FIG. 16taken in the direction of arrows BB.

FIG. 18 is a perspective view of a nut for use in the lockable nutsystem according to the present invention.

FIG. 19 is a reversed perspective view of the nut of FIG. 18.

FIG. 20 is a top sectional series view of a preferred embodiment of thelockable nut system in operation.

FIG. 21 is a perspective view of a further washer for use with alockable nut system of the invention.

FIG. 22 is a plan view of an alternative form of locking washer FIG. 23is a cross sectional view along A-A in FIG. 22.

FIG. 24 is an exploded view of a lockable nut system employing thelocking washer of FIGS. 22 and 23.

FIG. 25 is a cross sectional view of the assembly of FIG. 24 beforetensioning.

FIG. 26 is across sectional view of the assembly of FIG. 25 aftertensioning.

While standard threaded bar may be employed with the invention, therounded cross-sectional profile of the threads does not provide optimumtension capacity.

For this reason, it is preferred to utilise with the invention a moresubstantially profiled thread similar to an “Acme” style thread.

FIG. 1 illustrates portion of a threaded bar 40 having a planar face 41extending longitudinally of the bar on diametrically opposed sidesthereof.

The thread comprises part helical ribs 42 extending over thediametrically opposed part circular portions 43 of bar 40, the ribshaving a generally trapezoidal cross section as illustrated at the end44 of each part helical rib 42.

Threaded bar of the type illustrated in FIG. 1 is employed widely in themining industry for chemically anchored rock bolts and, as shown,comprises a single start thread.

FIGS. 2-4 show one embodiment of a nut locking system which may beemployed with the invention.

In the drawings nut 50 is a conventional long bodied nut utilised withbar 51 having a thread 52 extending generally in axially oppositedirections and a pair of generally planar side walls 53 therebetween. Apair of slots 54 is formed in, one or both end walls 55 of nut 50.

A locking member 56 has a cross sectional aperture with a shapecomplementary to the cross sectional shape of bar 51 such that thelocking member is slidable therealong but is prevented from rotation byengagement of planar side walls 57 of the sleeve with the side walls 53of the bar. The locking member 56 includes a pair of spigot likeprojections 58 axially engageable with slots 54 thereby effectivelylocking nut 50 against rotation on the bar 51.

In many applications such as diagonal or upright bracing, earth anchorsor the like, the locking member 56 may be maintained in engagement withnut 50 under the influence of gravity. Where it is not possible to relyon gravitational forces to maintain engagement, a screw threadedfastener 59 or the like may be utilised to prevent disengagement betweenthe nut 50 and locking member 56.

FIG. 5 shows a locking member in the form of locking washer 60 whichincludes tongue actuating tabs 61 which are shown here in a firstposition which is offset from a transverse plane of the locking washer60. Movement of the tongue actuating tab 61 to a second position whichis substantially co-planar with the transverse plane of the lockingwasher 60 causes tongues 62 to be displaced radially inwards.

The locking washer 60 also comprises finger actuating tabs 63 which arealso shown in a first position offset from the transverse plane of thelocking washer 60 but, in this case, offset in a direction opposite tothat of the tongue actuating tabs 61. The finger actuating tabs 63 maybe moved to a second position which is substantially co-planar with thetransverse plane of the locking washer 60 which results in a distal endof the fingers 65 being displaced radially outwards. The fingers are anexample of nut engaging elements. The finger actuating tabs are anexample of actuating elements. The locking washer 60 also includes acentral aperture 66 for receiving a threaded steel bar.

FIG. 6 shows a top view of the locking washer 60 of FIG. 5 whichhighlights the aperture 66 with tongue 62 and fingers 65 disposed aroundits periphery.

FIG. 7 is a side view of the locking washer of FIG. 6 taken in thedirection of arrow 67 and showing tongue actuating tab 61 offset fromthe transverse plane 68. Tongues 62 project and are apparent above thebody 69 of the locking washer 60. Likewise; fingers 65 are also readilyapparent.

FIG. 8 is a side view of the locking washer 60 of FIG. 6 taken in thedirection of arrow 70. This view shows the finger actuating tab 63offset from transverse plane 68 in a direction opposite to that of thetongue actuating tab 61. A single tongue actuating tab 61 and two fingeractuating tabs 63 are visible as are tongue 62 and fingers 65.

FIGS. 9 and 10 show the forces applied to the locking washer 60 duringuse and in one direction.

In use, the locking washer 60 is compressed between a first surface anda nut which threadably engages the threaded bar which is located throughaperture 66. As the nut is tightened, the locking washer is compressedbetween two surfaces. Force is applied in the direction of arrows 71 tofinger actuating tabs 63 while simultaneously an opposite force in thedirection of arrow 72 is applied to tongue actuating tab 61. The lockingwasher is comprised of material which permits movement of the tabs 61,63 from the first position shown to the second position shown in FIG. 10in which all the tabs are substantially co-planar with the body 69 andtransverse plane 68 of the locking washer 60.

When the tabs 61 move to the second position shown in FIG. 10, thedistal ends 73 of the tongues 62 are displaced radially inwardly. At thesame time as the finger activating tabs 63 are also displaced to thesecond position shown in FIG. 10, the distal ends 74 of the fingers 65are displaced radially outwardly.

The degree of displacement of the distal ends 73 of the tongue 62 isseen by a comparison of the length of the dimension arrows 75 in FIGS. 9and 10, respectively.

The operation of the locking washer is seen in side view at a rightangle or orthogonal view to that of FIGS. 9 and 10 in FIGS. 11 and 12,respectively. As the finger actuating tabs 63 are moved from the firstposition seen in FIG. 11 to the second position in FIG. 12 which issubstantially co-planar with the transverse plane 68 of the lockingwasher 60, the distal ends 74 of the fingers 65 are displaced radiallyoutwardly. The degree of displacement is seen by comparison of thedimension arrows 76 of FIGS. 11 and 12, respectively.

FIG. 13 is a perspective view of the locking washer 60 located on athreaded bar 80 and intermediate a castellated nut 77 and an immobilesurface 78. The castellated nut 77 is screw threadedly engaged with athread comprising part helical ribs 79. In use as the castellated nut 77is advanced towards the surface 78, locking washer 60 is compressedbetween the nut 77 and surface 78. The locking washer is preferablysited so that one of the tongues 62 is aligned with flat 81 and theother tongue 62 is aligned with the opposed flat (not visible). In thepresent view, the locking washer 60 requires rotation to achieve thisalignment. As the locking washer 60 is compressed, tongue activatingtabs 61 are flattened leading to displacement of the distal ends of thetongues 62 towards the flats 81 and subsequent contact between thosestructures. The engagement of the tongues 62 with the flats 81immobilises the washer 60 relative to the rod 80.

Simultaneously with compression of the locking washer 60, the fingeractuating tabs 63 are also compressed towards a transverse plane of thelocking washer 60 which causes distal ends of the fingers 65 to bedisplaced radially outwardly. At least one of the fingers 65 will seatin one of the slots of the nut 77 as exemplified by slot 82. Thepresence of a finger 65 in the slot 82 will prevent rotation of the nut77 relative to bar 80 and thereby lock the nut resisting or preventingits subsequent loosening. As used herein the references to “preventionof loosening” or the like are not intended to be construed as absolute,rather that in normal use environments, the nut locking system willprevent loosening of the nut under the influence of forces which mightotherwise be expected to increase a risk of loosening of the nut in use.It readily will be apparent to a person skilled in the art that withsufficient force applied by a spanner or the like, a nut may be loosenedagainst the locking resistance of the locking member, possibly causingdamage to the components of the lockable nut system and/or the thread onthe bar. It is clear that if adequate rotational force is applied to thenut, the integrity of the washer may be destroyed.

Preferably, the washer is made of a material such as a spring steel withsome degree of resilience which will allow the fingers to flex againstan inner surface of the nut as it is tightened and subsequently springinto the slot 82. The fingers may be angled to the direction of rotationof the inner surface of the nut 77 to thereby provide a camming effectin at least one direction to allow easy tightening of the nut with aramped radial inward displacement of the fingers. This camming orramping effect may be in one direction alone or, preferably, may be intwo directions so that the nut may be removed without damage to thelocking washer allowing re-use of the locking washer.

FIG. 14 is a side view of the arrangement of FIG. 13 in which a seriesof slots 82 is apparent in nut 77. The direction of rotation andtightening is shown by arrow 83 and a plan view of the components isvisible in FIG. 15.

FIG. 16 shows a part sectional view of the arrangement of FIG. 15 takenalong the line AA when the components of the locking system are fullyengaged. The locking washer 60 is substantially flattened with the tabs61, 63 forced into a transverse plane of the locking of the body of thewasher 60.

FIG. 17 is a part sectional view of the arrangement of FIG. 16 takenthrough the line BB showing slots 82 formed by adjacent legs 84 of thecastellated nut. The tongues 62 are shown forced into engagement withbar 80. Fingers 65A, 65B are shown located in slots 82 and therebyblocking rotation of the legs 84 of the nut and therefore the nutitself.

FIGS. 18 and 19 show views of opposite ends of a preferred embodiment ofa nut 85 having an internal thread 86 formed to engage the thread on abar. A first end 87 of the nut 85 includes a recessed region 88 with acontinuously toothed perimeter 89 formed internally in the nut. Therecesses between adjacent teeth of the outer perimeter 89 provide seatsto receive one or more locking teeth of a locking washer. In analternative form, the toothed perimeter may be on the outside of thenut. In such a case, however, movement of the finger activating tabwould need to cause ends of the fingers to be displaced radiallyinwards, not outwards, so that they engage the seats.

FIG. 20 shows a series of views demonstrating the function of the nut 85of FIG. 19 when used with five spaced teeth 90 of a locking washer 91.Adjacent recesses 92 on the nut 85 are separated by 22.5°. In the firstdrawing of FIG. 20, a tooth 90A is seated in a recess 92A. The seconddrawing of FIG. 20 shows the nut 85 rotated 7.5° with tooth 90B nowlocated in recess 92B. The process continues throughout the rest of thefigures as the nut 85 is rotated through 37.5° thereby providing each ofthe five teeth with a period during which they are located in a lockingrecess. The rod 80 is shown grasped by tongues 93. The teeth 90 areshown with ramped anterior and posterior edges 94 which allows the nutto be advanced or backed off without damaging the teeth. The teeth aredisplaced by a camming effect of the ramped edges so as to clear therecesses or seats. The arrangement shown provides a user with a widevariety of tightening options in use as a tooth engages a recess forevery 7.5° of turn. This feature is very important to coarse pitchedthreads which can require a massive increase in not tightening tongueover a relatively small degree of rotation of the nut.

Referring to FIG. 21, there is shown an embodiment of a locking washer160, wherein the tongue activating tab 161 and the finger activatingtabs 163 are offset from a transverse plane of the washer 160 in thesame direction. In order for the tongue 162 and fingers 165 to bedisplaced during use in an inward and outward direction, respectively,it is necessary that they be disposed in opposite axial directions. Thatis, the tongues 162 project in a first direction away from a transverseplane of the washer 160 and the fingers 165 project in the oppositedirection relative to the transverse plane. In this embodiment, thetongue activating tabs 161 and finger activating tabs 163 are stillshown as separate items. However, the washer may be dished or otherwisefabricated as a low truncated cone with a continuous apron forming thetabs whereby under compressing from a nut, the washer flattens toactuate both the tabs and fingers to engage the bar and nutrespectively.

In a modification of the locking member of FIG. 21, the washer. 160 maybe dished or otherwise formed as a low frustoconical member with theconvex surface extending in the same direction as teeth 165. In thisembodiment tongues 162 may be dispensed with but otherwise provideshouldered abutment 166 generally coplanar with the washer in use toengage the parallel sides of the threaded bar. Tongues 162 may be formedin the same direction as fingers 165.

When this latter embodiment is compressed by a nut against an anchoringsurface associated with the threaded bar coupling, the tongues 162, ifpresent, or the shouldered abutments 166 rotate radially inwardly toengage spaced recesses formed in the outer surface of a tubularextension (not shown) formed on the end of the nut.

The embodiment shown in FIG. 21 is however, the currently most preferredlocking member for a locking nut system according to the invention as itis the simplest to manufacture and by turning tongues 162 away from thenut to be locked, the depth of the finger engaging recess in the end ofthe nut is reduced thereby maximizing the area of engagement between thenut and bar threads.

In each of the embodiments of FIGS. 5 to 21, the ratio of the number offingers on the locking member or washer to the number of finger engagingrecesses associated with the nut is selected according to the pitch ofthe thread used in the nut/bar combination to accommodate large tonguevariations with coarse pitched threads in particular.

In a further embodiment, the locking member for the lockable nut systemmay comprise a planar disc-like body having a central aperturecomplementary to the cross sectional shape of a bar of the typegenerally shown in FIG. 1 whereby relative rotation between the bar andbody is prevented by engagement of the matching shapes. The disc mayhave one or more axially extending tabs which can be bent down with ahammer to engage in the slots 54 of nut 50.

In a still further modification of the sleeve-like locking member 56 ofFIGS. 2-4 or the disc-like body described above, they may includespigots or tabs with enlarged ends engageable in a slot or slots in anut 50, the slot or slots having complementary shapes to the enlargedend spigots or tabs, which when urged into the slots by a hammer or thelike, secure the nut and locking member against axial separation.

In its simplest form, the locking washer may comprise an oval centralaperture formed to prevent or resist rotation of the washer around a barand one or more teeth to engage locking nut. The teeth may be activatedby a tab or any suitable formation such as a conically shaped body whichflattens under compression and displaces the teeth radially outwardly.

FIGS. 22-26 show yet another embodiment of the invention.

As shown in FIGS. 22 and 23, the locking washer 170 having upstandingfingers 171 located about the outer circumference of washer 170. Fingers171 are formed with a generally tangentially directed portion 172 and agenerally radially inwardly directed portion 173 which tapersdivergently towards an upper end 174 thereof.

A pair of tongues 175 project inwardly and downwardly from an otherwisetoroidal body 176, which as shown in FIG. 23, if formed as an upwardlydished member with an inner edge 177 lying in a plane above outer edge178. Tongues 175 include inwardly tapered portions 175 a, the purpose ofwhich will be described later. Axially aligned with tongues 175 areupstanding alignment tabs 179, the purpose of which will be describedlater.

FIG. 24 shows an exploded view of a lockable nut assembly comprising athread rolled bar 180, the locking washer 170 of FIGS. 22 and 23 and alockable nut 181.

Lockable nut 181 is formed at its lower end 182 with an outwardlydivergent circular land 183 having a knurled pattern 184 or similarroughened surface.

As shown in FIG. 25, bar 180 may be secured in an aperture 185 in amounting bracket 186 or the like by first sliding locking washer 170over the free end 187 of bar 180 with tongues 175 (not shown) locatedadjacent opposed planar faces 180 a on bar 180 and otherwise extendinginto aperture 185.

FIG. 26 shows the final position of the respective components of thelockable nut assembly of FIG. 25 when nut 181 is tensioned on bar 180.

As nut 181 advances from the position shown in FIG. 25, the divergentlower end 182 of the land 183 initially engages the upper ends of tabs179 and urges the tabs outwardly to a slight extent. This “tilting” oftabs 179 causes a limited rotation of fingers 175 in an inward directionto grip the planar sides 180 a of threaded bar 180.

The lower end face 188 then engages the toroidal body 176 of lock washer170 adjacent the inner edge 177 thereof and as the nut is tensioned itforces the upwardly dished inner region of the washer into a positiongenerally co-planar with the upper surface 189 of bracket 186. At thesame time, tapered portions 175 a of tongues 175 (not shown) engageagainst the upper edge of aperture 185 and urge the tongues 175 intofirm engagement with planar sides 180 a of bar 180 to resist relativerotation therebetweeen. As the dished toroidal body 176 is flattened,fingers 171 rotate inwardly to engage the frustoconical end of nut 181formed by the tapered land 183.

Nut 181 is thus secured to resist loosening under vibratory loads by theupward restoring force of dished toroidal body 176 in combination withthe grip between the tapered edges of fingers 171 and the knurledsurface 184 of land 183.

As an alternative to the utilisation of spring steel for washer 170, itmay be made of a more malleable steel such as mild steel whereby thedished toroidal body 176 is plastically deformed under tension.

This plastic deformation causes fingers 171 to engage the frustoconicalland 183 and prevent loosening of the nut by the engagement between thetapered edges of fingers 171 and knurled surface 184 as well as therestoring forces resisting bending of fingers 171 in an outwarddirection as nut 181 tries to move axially away from washer 170.

In the embodiment shows in FIGS. 22-26, washer 170 is restrained againstrotation relative to bar 180 by engagement between tongues 175 andrespective planar sides 180 a of bar 180.

Throughout this specification and claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” or “comprising”, will be understood to, imply the inclusionof a stated integer or group of integers or steps but not the exclusionof any other integer or group of integers.

It will be readily apparent to a skilled addressee that manymodifications and variations may be made to the invention withoutdeparting from the spirit and scope thereof.

1. A lockable nut system for a threaded steel bar having a central axis down a length of said bar, and further having a non-circular cross-sectional shape with at least one planar side wall, said lockable nut system comprising: a screw threaded nut rotatably engageable on said threaded steel bar; and a tubular locking member slidably engageable on said threaded steel bar, said locking member being adapted in use to resist rotation about said bar, said nut and said locking member being axially non-deformably engageable, said engagement occurring using an extending member and an opening shaped to generally accept the extending member, further wherein said extending member extends in a direction generally parallel to said central axis of said threaded bar, engagement occurring without rotating said extending member and without rotating said opening shaped to generally accept said extending member, whereby in use said locking member resists rotation in at least one direction of said nut on said bar, and further wherein said locking member has a non-circular cross-section aperture wherein said non-circular cross-section consists of at least one interior planar side wall and is generally complementary to said non-circular cross-sectional shape of said bar wherein said bar consists of at least one planar face extending longitudinally of said bar.
 2. The lockable nut system in claim 1 wherein said locking member includes at least one inner side wall engageable with a respective side wall of said bar.
 3. The lockable nut system as claimed in claim 1 wherein said nut and said locking member are axially engageable by one or more socket and spigot formations on respective adjacent ends of said nut and said locking member.
 4. The lockable nut system as claimed in claim 1 wherein said locking member comprises a washer and said nut includes at least one washer engageable recess.
 5. A bracing system utilizing a lockable nut system, said bracing system comprising: a threaded steel bar having a non-circular cross-sectional shape with at least one planar side wall; a mounting bracket, wherein said mounting bracket includes an aperture, and further wherein said threaded steel bar extends through said aperture; a screw threaded nut rotatably engageable on said threaded steel bar, wherein said screw threaded nut includes an opening for receipt of an extending member; and a tubular locking member slidably engageable on said threaded steel bar, said locking member being adapted in use to resist rotation about said bar, wherein said locking member includes an extending member that extends in a direction generally parallel to the aperture within said mounting bracket, and further wherein said nut and said locking member are axially non-deformably engageable by insertion of said extending member of said locking member into said opening within said nut, engagement occurring without rotating said extending member and without rotating said opening shaped to generally accept said extending member, whereby in use said locking member resists rotation in at least one direction of said nut on said bar, and further wherein said locking member has a non-circular cross-section aperture wherein said non-circular cross-section consists of at least one interior planar side wall and is generally complementary to said non-circular cross-sectional shape of said bar wherein said bar consists of at least one planar face extending longitudinally of said bar; and further wherein said nut and said locking member prohibit said threaded bar from exiting said aperture of said mounting bracket without prior removal of said nut and said locking member from said threaded bar.
 6. The bracing system of claim 5 wherein said locking member includes at least one inner side wall engageable with a respective side wall of said bar.
 7. The bracing system of claim 5 wherein said nut and said locking member are axially engageable by one or more socket and spigot formations on respective adjacent ends of said nut and said locking member.
 8. The bracing system of claim 5 wherein said locking member includes at least one inner side wall engageable with a respective side wall of said bar.
 9. The bracing system of claim 5 wherein said nut and said locking member are axially engageable by one or more socket and spigot formations on respective adjacent ends of said nut and said locking member. 